Add Skins module

Nedjo has completed his initial work on the Skins module and we have created the initial four skins for Octavia, see issue octavia#3 (closed).

To finalize this work we need to add the module to the distribution.

Tasks

• Add Skins module to Octavia (done in original issue).
• Write an update to add it to existing sites.
• Add a dependency on Skins to the install profile's info file.